The Atmospheric Explorer-C (AE-C) spacecraft (designation: 06977 / 73101A ) was designed as a multi- sided polyhedron shaped frame with a mean diameter of 1.4 meter. AE-C weighed about 660 kg which ... included 85 kg of scientific instrumentation. AE-C was launched on 1973-12-16 and decayed on 1978-12-12.

The purpose of the AE-C mission was to investigate the uppermost layer of the earth's atmosphere, the thermosphere, with emphasis on energy transfer and other controlling processes. Photochemical processes related to the absorption of solar UV radiation were studied by making coordinated measurements of reacting constituents and the solar input. The payload included instrumentation to measure: Solar UV Fluxes, the Composition of Positive Ions and Neutral Particles, the Density and Temperature of neutral particles, positive ions and electrons, Atmospheric airglow emissions, Photoelectron Energy Spectra, and Proton and Electron Fluxes with particle energy up to 25 keV. The initial elliptical orbit of AE-C was altered many times in the first year of operations by means of an onboard propulsion system employing a 3.5-lb thruster.

PERIGEE CHANGES: The purpose of these changes was first to alter the perigee height to 129 km. Later the AE-C orbit was circularized and the perigee height was raised periodically, eventually to about 390 km height. By the natural drag action of the exosphere the orbit was then let to decay to 250 km perigee altitude.

LATITUDE COVERAGE: During the first year, the latitude of perigee moved from about 10 degrees north up to 68 degrees north and then down to about 60 degrees south.

LOCAL TIME COVERAGE: During this period of orbit modification about two cycles through all local times were completed.

OPERATIONAL MODES: The spacecraft could be operated in either of two modes: spinning at a nominal 4 rpm or despun to 1 revolution per orbit. The spin axis was perpendicular to the orbit plane. Power was supplied by a solar cell array. The spacecraft used a PCM telemetry data system that operated in real time or using an onboard tape recorder.